RE: [EXT] Re: [systemd-devel] [PATCH] libblkid: fix spurious ext superblock checksum mismatches

> -----Original Message-----
> From: systemd-devel <[email protected]> On
> Behalf Of Krister Johansen
> Sent: Tuesday, November 19, 2024 12:14 AM
> To: Lennart Poettering <[email protected]>
> Cc: [email protected]; Karel Zak <[email protected]>; systemd-
> [email protected]; David Reaver <[email protected]>;
> Theodore Ts'o <[email protected]>
> Subject: [EXT] Re: [systemd-devel] [PATCH] libblkid: fix spurious ext
> superblock checksum mismatches
> 
... 
> I may have done a poor job of explaining this.  This is ext writing its
> own superblock from the kernel, but reads seeing an potentially
> inconsistent view of that write.  O_DIRECT causes us to seralize with
> the locks ext4 holds when it writes the superblock, which prevents the
> read from observing a partial update.
> 
> It's not necessarily the partitioning tools causing this, but any
> filesystem level udpdate that modifies the contents of the superblock.

As I wrote before: I don't think the needless O_DIRECT fixes things some other code broke.